• Design & Manufacturing
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• 제13권2호
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• pp.6-11
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• 2019

In this study, we constructed the mathematical model to evaluate the roundness for plastic injection mold parts with complicated 3D curvatures. Mathematically we started off from the equation of circle and successfully derived an analytical solution so as to minimize the area of the residuals. On the other hand, we employed the numerical method the similar optimization process for the comparison. To verify the mathematical models, we manufactured and used a ball valve type plastic parts to apply the derived model. The plastic parts was fabricated under the process conditions of 220-ton injection mold machine with a raw material of polyester. we experimentally measured (x, y) position using 3D contact automated system and applied two mathematical methods to evaluated the accuracy of the mathematical models. We found that the analytical solution gives better accuracy of 0.4036 compared to 0.4872 of the numerical solution. The numerical method however may give adaptiveness and versatility for optional simulations such as a fixed center.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.499-505
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• 2001

The objective of the paper was to measure the pressure drop and to investigate the recirculation region of the conical orifices used in Kwang-yang Iron & Steel Company. The flow field with water used as a working fluid was the turbulent flow for Reynolds number of $2{\times}10^4$. The effective parameters for the pressure drop and the recirculation region were the conical orifice's inclined angle (${\theta}$) against the wall, the interval(L) between orifices, the relative angle of rotation(${\alpha}$) of the orifices, the shape of the orifice's hole(circle, rectangle, triangle) having the same area. It was found that the shape of the orifice's hole affected the pressure drop and the flow field a lot, But the other parameters did not make much differences to the pressure drop. The PISO algorithm with FLUENT code was employed.

• Journal of Biosystems Engineering
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• 제17권2호
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• pp.143-155
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• 1992

The aim of this study is to develop a general purpose algorithm for analyzing geometrical features of agricultural products and microscopic particles regardless of their numbers, shapes and positions with a computer vision system. Primarily, boundary informations of an image were obtained by Scan Line Coding and Scan & Chain Coding methods and then with these informations, geometrical features such as area, perimeter, lengths, widths, centroid, major and minor axes, equivalent circle diameter, number of individual objects, etc, were analyzed. The algorithms developed in this study was evaluated with test images consisting of a number of randomly generated ellipsoids or a few synthesized diagrams having different features. The result was successful in terms of accuracy.

• 한국항공우주학회지
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• 제36권9호
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• pp.884-890
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• 2008

본 논문에서는 원형 목표구역에 무인 비행체가 도달할 때 비행체의 지향각, 즉 속도 벡터의 방향과 비행체와 목표점과의 시선이 이루는 사이 각을 제어할 수 있는 일반화된 중기 유도법칙을 제안한다. 유도법칙의 도출을 위해 비행체의 운동을 비선형 미분 방정식으로 모델링하고 거리함수 가중치를 갖는 제어 에너지 최소화 문제로 접근하여 최적제어이론을 적용하였다. 결과적으로 원형 목표구역 도달 시 지향각 구속조건을 만족시킬 수 있는 최적 해를 도출한다. 해의 수렴성을 비롯하여 제안한 유도법칙의 특성에 대해 고찰한다. 수치적인 시뮬 레이션을 통해 전형적인 시나리오에 대해 제안한 유도법칙의 성능을 시범적으로 보인다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.69-72
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• 2007

Cellulose is a beneficial material that has low cost, lightweight, high compatibility and biodegradability. Recently electroactive paper (EAPap) on cellulose base was discovered as a smart material and actuator through ion migration and piezoelectric effect. Furthermore cellulose has a potentiality to apply the display material, because of its high reflectivity, flexibility and high transmittance. The various shapes and height patterns of the Cellulose acetate (CA) solution, such as circle and honeycomb patterns, were fabricated and observed by field emission scanning electron microscope (FESEM, S4300 Hitachi). The resulting pattern showed uniform size in the large area without defect. After stretching the CA film with saponification process in the sodium methoxide in methanol solution, Most of the compositions become one directional ordered nanofibers below 50nm.

• Journal of Multimedia Information System
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• 제6권4호
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• pp.185-190
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• 2019

For future autonomous cars, it is necessary to recognize various surrounding environments such as lanes, traffic lights, and vehicles. This paper presents a method of speed sign recognition from a single image in automatic driving assistance systems. The detection step with the proposed method emphasizes the color attributes in modified YUV color space because speed sign area is affected by color. The proposed method is further improved by extracting the digits from the highlighted circle region. A sequential cascade AdaBoost classifier is then used in the recognition step for real-time processing. Experimental results show the performance of the proposed algorithm is superior to that of conventional algorithms for various speed signs and real-world conditions.

• The Journal of Korean Physical Therapy
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• 제2권1호
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• pp.103-112
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• 1990

The intervertebral disc in the anterior portion of the function unit gives the spine its flexibility. The disc is attached closely to the vertebral endplates. Between these endplates and the annulus fibrosus, the nucleus pulposus of the lumbar disc is enclosed in a circle of unyielding tissues. Compressive pressure placed on the disc is dissipated circumferentially in a passive manner In response to the greater axial forced exerted on the lumbar spine in comparison to the cervical and thoracic spines, the nucleus pulposus has its greatest surface area in the lumbar spine. The intervertebral disc is not only structure that helps diss pate stresses placed on the spine. With flexion, extension, rotation, or shear stress, the load distribution on the function unit is shared by the intervertebral disc, anterior and posterior longitudinal ligaments, the facet joints and capsules, and other ligamentous structures like the ligamentum flavum, interspinous and supraspinous ligaments, which attach to the posterior elements of the functional unit.

• 수산해양기술연구
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• 제29권2호
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• pp.87-93
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• 1993

This paper is described on the positioning accuracy of GPS which has observed from November. 1991 to September, 1992 in Korean southeast coast. The main results give as follows. 1) A daily variance of positioning error is irregularly, and the average error of the latitude and the longitude are 15.1m, 22.7m respectively. 2) The usable satellites in Korean southeast coast from Panggojin to Chisepo are SV satellite number 2, 3, 11～21, 23～26 and sv 28, of all these sv 3, 16, 17, 23, 24 and 26 can be observed in all the area. 3) A circle of the average radius enclose 95% of the measurement points are 72.9m and the average shift distances from standard position are 34.6m. 4) The variation of PDOP(HDOP) at each measurement points are coincide with the one of distance error.

• 한국수학사학회지
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• 제33권4호
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• pp.223-236
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• 2020

We examine how the formulas of the area and the circumference of a circle related to pi in the ancient Egyptian and the Old Babylonian fields of mathematics have been controversial. In particular, the Great Pyramid of Khufu, Ahmes Papyrus Problem 48 and Moscow Mathematical Papyrus Problem 10 have raised extensive controversy over π. We propose the pi-theory of the Great Pyramid of Khufu as a dynamic symmetry based on Euclid's rectangle. In addition, we argue that the ancient Egyptian or Old Babylonian mathematics influenced Solomon's Molten Sea, Plato and Archimedes' pi.

• 분석과학
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• 제17권5호
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• pp.434-437
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• 2004

Alpha track technology can provide useful isotopic information of boron in the primary coolant water. In the quantitative analysis using the alpha track analysis, the shape or area of sample on the solid track detector becomes very important, especially for the analysis of liquid samples. In this research, a multi-dot plate has been developed for this purpose. The multi-dot plate provides fixed standard shape of the sample solution that stays inside of the printed circle, and consequently increases the reproducibility of the boron analysis.